1. Field of the Invention
The present invention relates in general to a continuously tunable optical pulse delay generator that employs a combination of group velocity dispersion and wavelength conversion to achieve a variable delay.
2. Description of the Background Art
Devices that allow for tunable optical pulse delays are of central importance to numerous fields including optical coherence tomography, ultrafast pulse metrology, radio frequency communications and optical communications. Given the tremendous variety of applications and settings where optical pulse delays are used, it is critical to have a variety of approaches for generating them. Currently there exist several options. The most straightforward approach uses bulk beam splitters and mechanical translation, forcing pulses to traverse a physical length that can be varied in a continuous fashion. The technique can be improved upon by using a resonant structure, such as a Bragg grating or microresonator, so that the pulses traverse the same length many times. Recent advances in fiber Bragg grating design and device packaging have resulted in the demonstration of tunable devices where one varies the group delay by either varying the wavelength of light or by physically changing the period of the grating. Using a fast device to switch pulses out of a recirculating loop is a good way to generate discretely variable delays. Each of the approaches described above has benefits and drawbacks in terms of maximum delay, accuracy of delay, wavelength of operation, speed of operation, pulse distortion, and conceptual complexity.